These are dark days for the Rubio campaign, and they might be his last. The confidence Sullivan has in a Florida victory does not extend much beyond Rubio’s staff and his longtime backers.

According to Republican consultants and political observers from Tallahassee to Orlando to Tampa to Miami, there’s virtually no evidence that Rubio has the robust campaign in place that’s needed to shrink — let alone overcome — Trump’s lead, which ranges from 7 to 20 percentage points, depending on the poll. For weeks, his team hasn’t blanketed known early voters with mail, and they weren't calling Republicans statewide until just a few days ago.

“There needs to be a flashing red light on Rubio’s headquarters: This is an emergency,” said Tony Fabrizio, a national Republican pollster and consultant who worked on Gov. Rick Scott’s two successful campaigns. “If I’m Terry Sullivan, I need to start thinking hard about pulling back from these other states as much as I can and making Florida a last stand. Florida is Rubio’s last stand. If he loses, he’s finished.”

The clock is ticking. Election day is March 15. And Floridians are already voting: 433,000 Republicans have cast early ballots — at least a fifth of the expected electorate.

By applying the three most recent Florida surveys’ polling averages to the early ballots cast, Rubio could be trailing Trump by as much as 62,000 votes or as few as 30,000. That’s not an insurmountable lead and, if Rubio were to suddenly start winning about 35 percent of all the GOP votes today to Trump’s 31 percent, the Florida senator would win the state.

The effort needed to do that, however, has yet to materialize in force.

Rubio’s campaign can’t completely pull out of competing for the 13 states and territories that vote March 5-12. Rubio not only needs the delegates to make the case that he could be a force at a contested convention, he needs to avoid another round of ugly losses that signal to Florida that a vote for Rubio is a wasted vote.

If Rubio loses here to Trump, the front-runner would have his first and largest batch of winner-take-all delegates— 99 —making him close to unstoppable on his way to the nomination.

Rubio’s team dismissed concerns that it hasn't done enough to set up for the Florida fight, with officials saying they just this week began shifting the operation into high gear.

On Sunday, surrogates including U.S. Reps. Ileana Ros-Lehtinen and Carlos Curbelo started phoning voters with pre-recorded messages. On Monday, volunteers began phone-banking specially identified voters. On Super Tuesday, Rubio made his election-night appearance in Miami to underscore the state’s importance. And on Thursday night, the campaign robo-called absentee-ballot requesters with a pre-recorded message from Rubio’s wife, Jeannette.

The campaign brought down 20 paid staffers this week and will have 14 more by Saturday, after which Rubio will be in the state almost daily — often in the swing area known as the I-4 Corridor that stretches from Tampa Bay to Orlando to Daytona Beach. The campaign also says it’s activating county chairs and friendly legislators who have political networks that will help get-out-the-vote operations.

Marco Rubio can't name states he's 'banking on' winning

Marco Rubio can't name states he's 'banking on' winning during an interview on CNN.

And the campaign for weeks has been robo-polling 4,000 Florida Republicans nightly in three-day samples to both gauge support and assemble demographic profiles of its target voters, the core of whom are college-educated married people with children (that is, people like Rubio). This week it finished opening its seventh field office in the state.

“It’s time to open the can of whoop-ass,” said one top Rubio backer, who acknowledged having concerns with the pace of the campaign in Florida. “I just hope it’s not too late.”

In interviews with consultants, campaign supporters and those familiar with Rubio’s thinking, his success might dependon four points — big turnout in his home county of Miami-Dade, increased super PAC support, minimizing Trump’s huge advantage in North Florida and winning Jeb Bush’s endorsement.

Rubio’s Super Tuesday appearance in Miami-Dade underscored the importance of the county to him. It’s Florida’s most-populous, with 354,000 Republicans, and more than 73 percent of them are Hispanic — nearly all of Cuban descent, like Rubio. Establishment Republicans remember how the county played a key role in giving Mel Martinez a 100,000-vote margin to beat Bill McCollum in the 2004 primary for U.S. Senate, a seat Rubio now occupies. Rubio backers hope for a repeat.

The strength of Miami-Dade’s Republican Party is no accident. One man gets outsize credit: Bush. And among older GOP voters — among the most reliable voters — he’s still well-liked. His refusal to endorse Rubio so far has unsettled some Republicans.

Though endorsements generally carry little weight, and Bush was polling poorly in Florida before he dropped out, Republican backers believe an endorsement of his old friend would energize longtime Republicans — especially those who fondly remember his term as governor — and at least create a news cycle of good media coverage that Rubio needs.

“I’m not saying we need Jeb, but let’s face it, he sure would help,” said one longtime Rubio backer. “We need to give him his space.”

No Florida candidate in modern times has been able to rely heavily on earned media from news events. Airtime in the state’s 10 major media markets is a must. And it’s expensive: about $1.5 million for a statewide weeklong buy for a candidate and $3 million to $5 million for a political committee.

Trump has announced a nearly $1 million TV buy for Florida. Rubio has made no such announcement, increasing the likelihood that he’ll have to rely on outside committees, which could cost as much as $10 million over two weeks. So far, the three political committees advertising in Florida are on pace to spend about half of what is probably needed. And two of the committees are anti-Trump only, which is of limited to use to Rubio.

Only Conservative Solutions super PAC overtly backs Rubio, and it’s strictly staying on air — not helping with voter turnout on the ground, where Rubio might need more help getting absentee voters to cast their ballots and getting early and election day voters to the polls. By contrast, Ted Cruz’s super PAC, and Bush’s before, helped turn out voters on the ground in some early states.

Rubio’s campaign said it held off on aggressively targeting absentee-ballot voters when Bush was still in the race because the two candidates shared voters with a similar profile. Rubio didn’t want to spend the money accidentally turning out Bush voters. But, as a result, that meant the campaign left the votes up to chance as thousands of absentee ballots poured in.

“This is an unconventional election with unconventional candidates in an unconventional year,” Sullivan said, “and this calls for unconventional campaign tactics.”

Rubio’s weakest point can be spotted on a map: rural North Florida. On Super Tuesday, Rubio was slaughtered by Trump in the one Alabama and two Georgia media markets that broadcast into Florida’s Jacksonville, Tallahassee and Pensacola areas. Trump won about 45 percent support in Thomasville-Tallahassee and in Brunswick-Jacksonville, where Rubio carried only 17 percent and 18 percent of the vote, respectively — third behind Cruz, according to an analysis from Florida-based MCI Maps. In the Mobile-Pensacola market, Trump won 47 percent of the vote while Cruz and Rubio tied at 19 percent.

Matthew Isbell, a Democratic data consultant with MCI Maps who analyzed the Georgia and Alabama results, said Rubio likely won’t lose as badly in some parts of North Florida because he’s better known in his home state and Republican voters in the suburban and urban areas of the big cities appear to be more Rubio leaning.

But the rural areas won’t be kind to Rubio, he said.

“You’ll see outside of the city centers the trashing of Rubio. It’s like Virginia; he did well in the suburban areas, but not the rural ones,” Isbell said. “The question Rubio has is one of margin: can his urban and suburban support override the rural decimation he faces.”

On Saturday, after making a speech just outside Washington, D.C., at the Conservative Political Action Conference, Rubio flies to Jacksonville to hold a rally with New Mexico Gov. Susana Martinez and then flies to Puerto Rico. That last stop is a twofer: Puerto Rico holds its primary Sunday, and Central Florida’s sizable Puerto Rican community will be watching.

Meanwhile, on Saturday, Trump will be speaking in Orlando at the same time he’s advertising on TV. With Trump’s momentum, money and grass-roots support, a number of establishment Republicans fear Rubio’s efforts to win Florida — let alone the nomination — might be too little, too late.

Rubio’s detractors and backers alike say he can’t be definitively counted out yet. Experts expect as few as 2 million and as many as 2.3 million Republicans to vote. So there are millions more votes left to be cast. There’s also another debate March 10 in Miami.

“There’s time for Marco. But not a lot,” said Republican consultant David “DJ” Johnson. A Tallahassee resident, he said he requested an absentee ballot and sat on it for days to see if he would be contacted by any campaign or super PAC. Nothing happened until Thursday, while he was on the phone with a POLITICO reporter.

“Well look at that, it’s about time,” he said by phone while checking his mail. But he found a problem with the piece: It was from the Conservative Solutions super PAC, and it just trashed Trump. It didn’t urge him to vote absentee or early. And it said nothing about Rubio.

As a former consultant for the Right to Rise super PAC, which backed Bush, Johnson said he became aware of a problem with Trump attacks: They didn’t work. But, he said, the combined TV spending from Conservative Solutions, Club for Growth and Our Principles super PAC could make a difference if it’s done in a sustained and broad way.

“It’s a must to be on TV in Florida,” said Johnson. “But someone has to be doing a ground game and banking votes. And so far I don’t see it.”